Hi Joanna

Have you considered systemic Candidiasis in the sinus? It's possible to have an infection occur from previous antibiotic use, which although treated and apparently cleared up, may still reside in the sinus area to reoccur later - often months - even years after the original infection.

Symptoms may be subtle such as a mildly blocked nose which moves from one nostril to the other when you turn while sleeping. The symptoms may increase during times when the immune system is weak and spread to the mouth and throat area.